The present invention relates to blades of turbomachines, such as blowers, compressors, pumps and fans of the axial, semi-axial or radial type. The working medium (fluid) may be gaseous or liquid.
More particularly, this invention relates to at least one blade of a turbomachine. The respective blading is situated within a casing, which confines the passage of fluid through a rotor and, if applicable, a stator in the outward direction. While a rotor comprises several rotor blades attached to a rotating shaft and transfers energy to the working medium, a stator comprises several stator blades mostly fixed in the casing. In specific cases, such as propellers and fans, no casing exists.
The aerodynamic loadability and the efficiency of turbomachines, for example blowers, compressors, pumps and fans, is limited in particular by the growth and the separation of boundary layers in the area of the rotor and stator radial gaps near the walls of the annulus. The state of the art only partly provides solution to this fundamental problem. Accordingly, a bend, sweep or dihedral is imparted to the blading by way of a special shape of the blade stacking axis, for example, to positively influence the peripheral zone flow (see EP 0 661 413 A1, EP 1 106 835 A2, EP 1 106 836 A2). Also, attempts exist to improve the peripheral flow at the ends of blades with firm wall attachment by very local enlargement of the profile depth only (see EP 0 833 060 A2). Moreover, the latter concept is restricted to the same maximum profile thickness of the individual blade sections. In particular for the flow conditions at a blade end with radial gap, the known solutions are not adequate and, therefore, of limited effectiveness only.
The state of the art is disadvantageous in that the respective blade designs frequently are very complex in relation to the degree of flow improvement achievable and, with regard to the mechanical strength, can frequently only be realized in a machine if significant compromises in the form of the profile are accepted. Moreover, a profile depth enlargement limited to the gap-near blade sections, as in the state of the art, will not maximize the influence on the gap flow. This is due, in particular, to the unfavorable distribution of the shares of profile depth enlargement apportioned to the leading and trailing edges. It is also particularly attributable, however, to the small area of the blade height selected for profile depth enlargement. A run-out of the profile depth enlargement extending further into the area of the blade center does not exist. Accordingly, the state of the art provides for an improvement in efficiency and stability of the turbomachine, but to a relatively small degree only. Consequently, the possible reduction in the number of components is only small.